'identifier' : more than one GUID associated with this object
The __uuidof operator takes a user-defined type with a GUID attached or an object of such a user-defined type. This error occurs when the argument is an object with multiple GUIDs.
Example
struct __declspec(uuid("00000001-0000-0000-0000-000000000000")) A { }; struct __declspec(uuid("{00000002-0000-0000-0000-000000000000}")) B { }; template <class T, class U> class Foo { }; typedef Foo<A,B> MyBadFoo; typedef Foo<A,A> MyGoodFoo; void bar(void) { __uuidof(MyBadFoo); // error C2788 __uuidof(MyGoodFoo); // OK }